The long term objective of this proposal is to devise a method for the large scale biosynthesis of a negative regulator of mammalian cholesterol biosynthesis. This compound has potential use in the treatment of hypercholesterolemia and may reduce the occurrence of atherosclerotic heart disease. As a step toward achieving the biosynthesis of this compound, we propose to isolate the gene encoding a key enzyme required for the synthesis of this regulatory molecule, determine the complete nucleotide sequence of the gene and the location of transcriptional initiation. The gene will be cloned from the yeast Saccharomyces cerevisiae by complementation of an auxotrophic mutation in that gene or by overcoming the effects of a specific enzymatic inhibitor through gene dosage. The clone, and the information provided by this sequence, will be used to construct a microbial strain capable of producing the regulatory molecule. Such a strain may allow commercial scale production of the compound for further testing and development.